1. Field of the Invention
The present invention generally relates to electronic equipment having an overcurrent protection fuse, and more particularly to electronic equipment having a fuse provided on a signal ground line.
2. Description of the Related Art
In recent years, users occasionally use car stereos by respectively connecting external power amplifiers thereto so as to enjoy audio from the car stereos with higher quality at a larger volume. In this case, audio signals are amplified by an amplifier circuit provided in the power amplifier. Then, sounds represented by the amplified signals are outputted from speakers. That is, as shown in FIG. 3, the car stereo outputs audio signals from a pre-amplifier output terminal 1a. The audio signals are transmitted to the power amplifier 3 through an RCA cable 2 connected between this pre-amplifier output terminal 1a and an input terminal 3a of the power amplifier 3. Subsequently, the power amplifier 3 amplifies the audio signal, which is transmitted from the car stereo, at an internal amplifier circuit thereof and outputs the amplified signal to the speaker 4. Consequently, a user can enjoy sounds represented by the power amplifier 3.
Meanwhile, when a user uses both of a car stereo and a power amplifier in a car, it is necessary to connect the power line (corresponding to the positive terminal (+)) and the ground line (corresponding to the negative terminal (xe2x88x92)) of a battery to each of the car stereo and the power amplifier. However, because it is usual that an operation of connecting this battery thereto is performed by using power cables 6, there is a fear that miswiring may occur.
Usually, the car stereo and the power amplifier are constructed in such a way as not to operate even when miswiring occurs in the power cables 6. However, the car stereo and the power amplifier may operate when power or a ground is supplied thereto from a path other than the power cables 6. Hereinafter, a representative example of this is described with reference to FIG. 4. FIG. 4 illustrates the case that the power cable 6 serving as the ground line to be connected to the power amplifier 3 of FIG. 3 is not connected thereto. In this case, the power amplifier 3 is not supplied with a ground, because the power cable 6 serving as the ground line is not connected thereto. However, as illustrated in FIG. 4, the grounds of the car stereo 1 and the power amplifier 3 are connected to each other through RCA cable 2. Therefore, the power amplifier 3 is connected to the ground line through the RCA cable 2 and the car stereo 1. Consequently, although the power cable 6 serving as the ground line is not connected to the power amplifier 3 shown in FIG. 4, this power amplifier 3 normally operates by utilizing a ground supplied thereto through the RCA cable 2.
However, in this case, electric current I2 consumed by the power amplifier 3 cannot return directly to the battery through the power cable 6, as illustrated n FIG. 3. Thus, the current I2 returns to the battery 5 through the RCA cable 2 and the car stereo 1, as illustrated in FIG. 4. Therefore, in addition to the current I1 consumed by the car stereo 1, the electric current I2 additionally flows through the car stereo 1.
Because the current I1 is a known current for the car stereo 1, a sufficient current capacity is ensured at a design stage. On the other hand, the current I2 is an unknown current, which is caused by miswiring, for the car stereo 1. Moreover, the current I2 flows through a signal ground pattern constituted by a relatively thin pattern. Thus, a sufficient current capacity is not ensured for the current I2. Therefore, in the car stereo 1, a thin part of the signal ground pattern provided therein, that is, a part having a small current capacity is burnt out owing to the current I2. This causes a fault of the stereo. Especially, when all currents to be passed through electronic equipment, such as the power amplifier 3, which consumes large current, flow thereinto, this inflow causes the breakage of electronic components in addition to the burning-out of the signal ground pattern.
A non-limiting aspect of the present invention is to solve the aforementioned problem.
To achieve the above mentioned aspect, there is provided electronic equipment that comprises a terminal for inputting or outputting signals to be used in a circuit provided therein. This terminal is connected to the circuit through at least a signal line and a signal ground line. The electronic equipment further comprises a fuse provided on the signal ground line.